The present invention relates to space vehicle attitude control systems for precisely pointing the sensitive axis of scientific instruments at any arbitrary target in space in general and, in particular, to an attitude control system employing strapped-down gyroscopes, a sun and star tracker, and a method and error correction apparatus for compensating for gyro drift, integrator drift, scale factor error, gyro input axis triad non-orthogonality and gyro input and axis-optical axis misalignment.
A number of systems have been employed in the past to perform this function. They are of three basic types using either star-trackers to identify and lock-on to known stars at or near a target, gyroscopes with (or without) accelerometers on a stabilized platform to provide an inertial reference from which the target may be located, or a combination of gyroscopes and star-trackers wherein the gyros stabilize the vehicle and provide coarse pointing guidance while the star-tracker holds the vehicle on target. A programmable (general purpose) digital computer is usually required for the first two types of these systems.
The prior known systems, however, suffer from either being overly complex (hence, expensive and unreliable) or lacking the accuracy and precision demanded by experimenters, or both.